In current rotatable and telescopic work machines, such as material handling machines, the overall height of the work machine is generally increased due to the “stacking” of various components, such as, the rotation means, cab, engine and telescopic boom. The significant height of the work machine limits its ability to enter certain work areas or buildings that have space constraints at access doors, service entries, and the like. Further, the positioning of the various components on some of these work machines causes weight distribution problems as the center of gravity is elevated and focused. Weight distribution problems can reduce efficiency or performance of the work machine. Additionally, an elevated center of gravity reduces stability of the work machine and reduces operator visibility as the various components are placed at higher levels. Visibility may be further impaired on some of these work machines when the telescopic boom is mounted on one side of the cab and blocks the operator's view of a work implement, attached to the telescopic boom, or the surrounding terrain.
One known rotatable and telescopic work machine, U.S. Pat. No. 4,216,869 issued to John J. Grove on Aug. 12, 1980, discloses an industrial crane that has a chassis mounting a housing. The chassis has a horizontal deck with a central well that provides access to a bearing for a rotatable upper works. The upper works has a portion that extends into the well and to the bearing. The upper works also includes a cab directly over the bearing, a boom support rearward of the cab, an engine rearward of the boom support and above the chassis, and a lifting boom journalled to the boom support rearward of and extending forwardly over the cab. The boom, cab, and engine have their lateral centers in line along the median plane of the upper works. The median plane of the upper works coincides with the median plane of the chassis when the upper works is in the forward or reverse position. Although the positioning of a portion of the upper works within the well assists in lowering the center of gravity of the crane, the positioning of the engine above the chassis distributes weight at an elevated level that nullifies the low center of gravity benefits. Additionally, the positioning of the engine rearward of the boom support may create an unfavorable distribution of weight at the rear of the crane, lowering its efficiency and stability. Further, the positioning of the engine in such a manner results in a low clearance height for the swing radius of the boom and effectively blocks all rear visibility for the operator during operation of the crane.
Other rotatable work machines that do not have telescopic booms, such as excavators, may also have similar deficiencies as those work machines with telescopic booms. For example, U.S. Pat. No. 4,102,461 issued to Ingebret Soyland on Jul. 25, 1978, discloses a rotatable excavator with a low center of gravity. The excavator includes a vessel-like lower frame with a vertical side wall and a bottom wall that forms a support plate. An upper frame is mounted on the lower frame for rotation about a vertical axis. The upper frame carries a cabin, a boom, and a bucket assembly. The engine and other heavy equipment components for operating the excavator along with the rotation means are secured to the underside of the upper frame in a suspended manner. In order to rotate the upper frame, along with the boom, bucket assembly, and engine, the rotating means engages with a gear in the lower frame. Although the center of gravity is lowered and visibility is improved in this excavator design, the height of the excavator is still defined by the full height of the lower and upper frames due to the upper frame being “stacked” on the lower frame. While this may not be as great an issue in a rotatable excavator that typically works in an external environment, any increase of height in a rotatable and telescopic work machine lowers its accessibility to enclosed work areas or buildings that have space constrained entryways.
The present invention is directed to overcoming one or more of the problems as set forth above.